Not Applicable.
Not Applicable.
1. Field of Invention
The present invention relates generally to control systems and, more particularly, to systems for controlling a solenoid valve driver used to drive a valve of a compression cylinder.
2. Description of the Background
Hydraulic presses find wide application in modem industry, such as in the manufacture of galvanized steel studs. Typically, the manufacture of studs includes passing the studs through a multi-pass rollforming machine. While being rollformed, the studs are punched with holes of various shape and size. Thereafter, the studs are cut to their desired length. The punch and cutoff systems are typically activated by flying hydraulic presses.
In such hydraulic presses, valves are commonly used to govern the flow of hydraulic fluid into and out of the compression cylinders of the hydraulic presses. The shifting of the valve spools of the valves is ordinarily controlled by valve drivers, which are typically solenoids. In the prior art, the solenoids are typically powered by voltage-amplified control signals. These control signals, however, are typically of a low power. Thus, the dwell time of the solenoid necessary to fully shift the valve spools of the valves must be increased. As a result, the valves open and close relatively slowly. Moreover, the mass, and thereby the size, of the valves must be kept small so as to not further slow the opening and closing of the valves. This, in turn, limits the available sizes for the valve openings. The limitations in the size of the valve openings and the shifting of the valve spools limit the size of the hydraulic compression cylinders that can used in the hydraulic press system. As a consequence, smaller compression cylinders are typically used, which must be operated at higher operating pressures in order to achieve the same force as otherwise achievable with a larger cylinder. In modern rollforming applications, for example, the operating pressure for the hydraulic punch and cutoff systems typically range from 1600 PSI to 3600 PSI, with dwell times of approximately 0.050 to 0.100 milliseconds. At such high operating pressures, however, mechanical components of the hydraulic presses tend to wear out or break quickly.
Accordingly, there exists a need for a manner to minimize the dwell time of the valve driver of a hydraulic press system in order that the operating pressure of the press may be reduced.
The present invention is directed to a control system for controlling a solenoid valve driver used to drive a valve of a compression cylinder, such as a hydraulic compression cylinder or a pneumatic compression cylinder. According to one embodiment, the control system includes power supply, a controller, and a first switching device having a first terminal connected to a first output terminal of the power supply, a second terminal connected to a coil of the solenoid valve driver, and a control terminal connected to a first output terminal of the controller.
The present invention provides a manner in which to reduce the dwell time of the solenoid valve driver of a hydraulic press, thereby permitting the use of larger compression cylinders, which in turn permits a concomitant reduction in the operating pressure of the press. Consequently, by permitting a reduction in the operating pressure of the press, the life of mechanical components of the press may be extended. The present invention also permits faster production line speeds, which translates to increased productivity, because the press may operate at a higher speed because the dwell time of the valve driver is reduced. These and other benefits of the present invention will be apparent from the detailed description of the invention hereinbelow.